Wales and Scarlets fly-half Rhys Priestland has suffered a devastating injury blow that will rule him out for the rest of this season.

The 25-year-old will miss the entire Six Nations Championship after snapping his Achilles tendon during the Scarlets' Heineken Cup clash against Exeter three days ago. Priestland, who has 22 caps, also looks set to miss out on the British and Lions' tour of Australia next summer in the latest injury setback for Wales as they prepare to launch their Six Nations title defence. Priestland's injury is to his left Achilles, with the Scarlets confirming that he underwent surgery this morning.

Scarlets head coach Simon Easterby said: "It's a big blow for Rhys and for our region to lose a player of his quality and influence in our team. He was coming through well in the last couple of (Wales) games of the autumn, put in a strong performance against Australia and was making a real impact on our game against Exeter, so it is very difficult for him to take. But he will get plenty of support from here throughout the injury period."

Scarlets medical chief Andy Walker added: "The surgery was undertaken this morning at the Vale Hospital and has gone very well. It's a difficult injury, but we have been fortunate to have had the injury assessed and repaired surgically so promptly, and by a very experienced ankle and foot specialist.

"Rhys' surgery was performed by a new keyhole surgery technique which is non-invasive and will aid his recovery and allow him to get into rehab with our medical team at a quicker stage. The anticipated time off the field is around six months, but it all depends on the individual and how his rehab goes in the interim."

Wales' recent autumn Test campaign was riddled by injuries as they lost four successive games against Argentina, Samoa, New Zealand and Australia. And Rob Howley, in interim coaching charge for the Six Nations campaign while Wales head coach Warren Gatland concentrates full-time on heading up Lions tour preparations, has been dealt another major setback with news of Priestland's injury.

Prop Aaron Jarvis is already out of the Six Nations campaign, while lock Alun-Wyn Jones and flanker Dan Lydiate are set to play only limited parts, at best, while they continue their respective recoveries from shoulder and ankle trouble.

Full-back Leigh Halfpenny and centre Jamie Roberts, meanwhile, are battling for full fitness ahead of the tournament, which Wales start against Ireland in Cardiff on February 2, while wing George North (hip injury) has not played since the Samoa game almost four weeks ago.

Priestland was a driving force behind Wales' outstanding push to reach the World Cup semi-finals in New Zealand last year, form which he carried over into last season's Six Nations when Wales were crowned Grand Slam champions.

Although the latter half of 2012 has seen him struggle to reproduce that form, he remained a key member of the Wales team, starting three of the autumn games and going on as a substitute against Samoa.

With Priestland sidelined, Howley would appear to face a choice between Perpignan's James Hook and Ospreys No.10 Dan Biggar for the Six Nations campaign. And there was every chance that Priestland would have made the Lions tour, a dream that now appears to have been cruelly shattered.